Distributions of functional groups in plasma polymerized allylamine films by scanning force microscopy using functionalized probe tips

Thin films of poly(allylamine) on silicon were prepared by polymerization of allylamine in a pulsed glow-discharge plasma reactor. The films were characterized by surface plasmon spectroscopy (SPS) and waveguide mode spectroscopy (WAMS), as well as by X-ray photoelectron spectroscopy (XPS) and FT-IR spectroscopy. It was shown that by variation of the duty cycle the film thickness as well as the content of amino and nitrile groups could be controlled. Scanning force microscopy (SFM) measurements with chemically functionalized tips led to a qualitative correlation of adhesion forces with the content of amino groups. Laterally resolved adhesion force measurements indicated the presence of a heterogeneous local environment of the amino groups, with patches exhibiting differences in hydrophobicity on a sub-50-nm scale.